Recently, communication devices such as health monitoring devices employing an RFID (Radio Frequency Identification) and a wearable computer are being used. Such devices are used in contact with the human body over a long period of time, unlike a mobile phone used in a close distance for a short period of time. Therefore, electromagnetic waves generated at frequency bands used in such communication devices may more affect the human body, so that the effect of electromagnetic waves on the human body has significantly become important.
For the present, the effect of electromagnetic waves on the human body has not been clearly revealed, but, it has been reported that there is a possibility of the electromagnetic waves influencing various diseases such as leukemia, a brain tumor and a headache. Moreover, when the body is exposed to the electromagnetic waves for a long period of time and/or in a very close distance, the effect may be considerably increased.
Technologies in regard to the effect of electromagnetic waves on the human body have been mainly about a mobile phone used close to the head part.
As conventional technologies for reducing electromagnetic waves regarding the mobile phone, there have been introduced an electromagnetic absorber, a technique of using an electromagnetic interference (EMI) paint, and a technique of changing the structure of a radiator such as antenna. Further, there is a technique of using electromagnetic bandgap (EBG), which engraves a periodic metal pattern on a substrate made of a dielectric and the like to thereby change electromagnetic characteristics of a radiator.
However, communication devices used in contact with the human body such as a wearable device are gradually increasing, and thus in order to prevent a bad influence of such devices on the body, more studies for blocking or reducing the electromagnetic waves are required.